Electronic toll collection systems are commonly used to facilitate the collection of a toll from a moving vehicle traveling on a toll-roadway.
Automatic Vehicle Identification (“AVI”) is the process of determining the identity of a vehicle on the roadway. Typically, electronic toll systems use a series of antennas that are mounted near the roadway which provide coverage zones that extend the width of a lane. Radio frequency (“RF”) transponders are mounted on or within a vehicle to communicate with the antennas. A roadside AVI reader typically interrogates the transponder using the antenna. Typically, the roadside reader is connected to a vehicle detector and imaging system which permits vehicles to be detected, classified, and photographed, and the license plate numbers analyzed in order to permit the operator of the toll system to apply to appropriate charges to the owner of the vehicle.
In order to ensure proper tracking and identification of vehicles, it is often necessary to identify which lane a vehicle is located in. For example, lane identification is often used to separate vehicles that are equipped with transponders from vehicles that are not equipped with transponders in order to associate the video images of their license plates with the vehicles that are not equipped. In order to do so, the electronic toll collection system must clearly identify where the subject vehicle is located within the multi-lane roadway.
Lane identification is made difficult since RF capture zones may overlap. Such overlap is typically by design since it is necessary to ensure that there are no dark spots along the width of the roadway where the vehicle will be outside of a coverage zone.
It is therefore desirable to provide a vehicle position determination system and method having improved accuracy for determining the position of a moving vehicle having a transponder in an electronic toll system.